The proposed work involves three related efforts. The first is a performance of a controlled clinical trial of three informational interventions: newsletters, reports comparing an individual physician with his peers, and personal contact by faculty members. The effect of these interventions will be measured in terms of changes in the physicians' decisions with respect to a selected set of common medical decisions. The overall goal of this effort is to reduce the variance between observed practice and target ideals and to identify physician factors that explain this variance. Secondly, we plan to perform an experimental trial of computerized reminders, newsletters and peer comparison on physicians in private practice in order to establish the external validity of the studies performed at the Wishard Memorial Hospital and to compare the decision strategies of private academic practice. The final effort is intended to reduce the uncertainty and the probability estimates required to make treatment decisions about atypical chest pain, cardiomegaly, headache and other topics to be chosen. The probability estimates will be derived from some measures and observations made on a sample of patients from our clinical population. Algorithms will be derived from these probability estimates, and the effect of the presentation of probability estimates and of these algorithms on physicians' decision variance will be measured.